Haggai 2:6 For thus saith the LORD of hosts; Yet once, it is a little while, and I will shake the heavens, and the earth, and the sea, and the dry land;
7 And I will shake all nations, and the desire of all nations. ...
21 Speak to Zerubbabel, governor of Judah, saying, I will shake the heavens and the earth;
22 And I will overthrow the throne of kingdoms, and I will destroy the strength of the kingdoms of the heathen; and I will overthrow the chariots, and those that ride in them; and the horses and their riders shall come down, every one by the sword of his brother.
This prophecy is like a weather-report, a storm-warning, from the future, sent by the all-knowing, all-seeing God.
Why did He send such a warning? to frighten us?
Of course not. God doesn't desire to frighten His children.
The purpose of the warning is so that we will not be taken by surprise, but rather be ready for what's coming in God's plan, and in that storm walking faithful and close to Jesus.